The present invention relates to a method and apparatus for scrambling digital samples of multimedia data, e.g., such as audio or video data samples, such that the content of the samples is degraded but still recognizable. For example, the invention is suitable for use with digital broadcast streams and digital storage media, such as compact discs (CDs) and digital video discs (DVDs). The number of least significant bits (LSBs) scrambled in each sample is selected such that the scrambled samples are degraded but still recognizable.
Schemes for communicating and storing digital data have become increasingly popular, particularly in the mass consumer market for digital audio, video, and other data. Consumers may now send, receive, store, and manipulate digital television, audio and other data content, such as computer games and other software, stock ticker data, weather data and the like. This trend is expected to continue with the integration of telephone, television and computer network resources.
However, in many cases it is desirable to control or monitor the use of such digital data. In particular, copyright holders and other proprietary interests have the right to control the distribution and use of their works, including audio, video and literary works.
In a copyright management system where audio and video content are to be protected, it would be desirable to provide data scrambling to deter theft of the content while it is in transit. The distance of transit can be half way around the world, as with delivery on the Internet, or millimeters, such as within a DVD player's internal data transfer from disc to DAC (Digital to Analog Converter).
It would be desirable to provide a method and apparatus that renders the audio/video content unsuitable for listening/viewing purpose but sufficient for identification of an audio/video passage, e.g., during fast forward playback, when there is insufficient time to descramble the samples.
It would be desirable to scramble bits in successive frames of digital data samples according to a scrambling key, where the scrambling key is embedded into the scrambled signal.
It would be desirable for the scrambling key to be associated with the scrambled data to allow the scrambling key to be easily changed without modifying the player (e.g., DVD or CD player) on which the data is played.
It would be desirable to scramble data such that the content is degraded sufficiently so that it no longer has any significant commercial value, but, at the same time, is perceptually satisfactory for player functions such as cueing and fast forward.
The scrambled data should not damage the video or audio equipment even if it is played through any video or audio playback system. Some randomly scrambled waveforms can result in such damage, e.g., to speakers or circuitry.
It would further be desirable for the scrambled data to be any conceivable digital data.
It would be desirable for the data to be scrambled at any time, including, for example, when the data signal is created (e.g., during a recording session for an audio track), when the data signal is being distributed (e.g., during a broadcast, or during manufacture of storage media such as compact discs), or when the data is being played (e.g., on a player in a consumer's home).
The present invention provides a system having the above and other advantages.